Perimeter coverage scheduling in wireless sensor networks using sensors with a single continuous cover range

In target monitoring problem, it is generally assumed that the whole target object can be monitored by a single sensor if the target falls within its sensing range. Unfortunately, this assumption becomes invalid when the target object is very large that a sensor can only monitor part of it. In this paper, we study the perimeter coverage problem where the perimeter of a big object needs to be monitored, but each sensor can only cover a single continuous portion of the perimeter. We describe how to schedule the sensors so as to maximize the network lifetime in this problem. We formally prove that the perimeter coverage scheduling problem is NP-hard in general. However, polynomial time solution exists in some special cases. We further identify the sufficient conditions for a scheduling algorithm to be a 2-approximation solution to the general problem, and propose a simple distributed 2-approximation solution with a small message overhead. Copyright © 2010 K.-S. Hung and K.-S. Lui.published_or_final_versio

On perimeter coverage in wireless sensor networks

Many sensor network applications require the tracking and the surveillance of target objects. However, in current research, many studies have assumed that a target object can be sufficiently monitored by a single sensor. This assumption is invalid in some situations, especially, when the target object is so large that a single sensor can only monitor a certain portion of it. In this case, several sensors are required to ensure a 360 coverage of the target. To minimize the amount of energy required to cover the target, the minimum set of sensors should be identified. Centralized algorithms are not suitable for sensor applications. In this paper, we describe our novel distributed algorithm for finding the minimum cover. Our algorithm requires fewer messages than earlier mechanisms and we provide a formal proof of correctness and time of convergence. We further demonstrate our performance improvement through extensive simulations. © 2006 IEEE.published_or_final_versio

On perimeter coverage in wireless sensor networks with minimum cost

One of the major applications of sensor networks is tracking and surveillance. Very often, a single sensor is sufficient to monitor a single target. However, when the object is very large, several sensors have to work together to monitor the object continuously. In this paper, we study how to identify a set of sensors that can cover the perimeter of a large target with the minimum cost. We develop a novel distributed algorithm that requires fewer messages than existing mechanisms. Our algorithm can be extended to solve the problem when the sensor range is adjustable. We provide a formal proof of correctness and convergence time analysis of our algorithm. We further demonstrate the performance through extensive simulations. © 2011 Inderscience Enterprises Ltd.postprin

On attack-resilient wireless sensor networks with novel recovery strategies

proceedings of the IEEE Wireless Communications and Networking Conference, 2009, p. 1-6In a wireless sensor network (WSN), when an adversary physically captures one or more sensor nodes, all the information stored on these nodes may be exposed completely. Consequently, the adversary can use the information to attack the remaining part of the network. In this paper, we investigate the effects of different node capture attack patterns on state-ofthe-art key management schemes. We find that a compromised WSN can be made resilient to such attacks by introducing new resources, such as new nodes and new keys. Based on this observation, we propose two recovering strategies, namely, link replacement strategy and node replenishment strategy, to replace the compromised links and the functions of the compromised region, respectively. Simulation results indicate that our proposed strategies can improve the network resilience of a compromised WSN significantly with a small amount of additional resources. ©2009 IEEE.published_or_final_versio

Relatório de estágio pedagógico em educação física realizado na Escola Básica 2º e 3º Ciclos Dr. Eduardo Brazão de Castro

O presente Relatório de Estágio pretende descrever e refletir as atividades desenvolvidas ao longo do Estágio Pedagógico (EP), no ano letivo 2014/2015 na Escola Básica dos 2º e 3ºciclos Dr. Eduardo Brazão de Castro. O objetivo deste relatório foi fundamentar e refletir as opções metodológicas e didáticas realizadas no seguimento das quatro áreas de intervenção das linhas programáticas do EP: a prática letiva, as atividades de integração no meio, as atividades de intervenção na comunidade escolar e as atividades de natureza científico-pedagógica. A prática letiva foi sem dúvida umas das componentes principais deste estágio, onde durante um ano letivo conduzimos o processo ensino-aprendizagem numa turma de 9º ano. Para tal, seguimos de forma cíclica as fases de planeamento, realização e controlo e avaliação da nossa intervenção. A prática letiva compreendeu ainda a organização e conceção de um instrumento de observação para a assistência às aulas. As atividades de integração no meio compostas pelas atividades no âmbito da direção de turma, compreendem a caraterização da turma e o estudo de caso. Estas atividades proporcionaram uma análise minuciosa sobre a turma, fundamental para adequar as estratégias pedagógicas. Estas atividades culminaram com a ação de extensão curricular, onde se promoveu a aproximação entre a escola e os encarregados de educação através de uma atividade de promoção de hábitos de Atividade Física (AF) e de estilos de vida saudáveis. Relativamente à atividade de intervenção na comunidade escolar, dirigida para toda a comunidade educativa, teve como objetivo a promoção de AF através da realização das “IV Olimpíadas Brazão de Castro”. Finalmente, as atividades de natureza científicopedagógica tiveram como propósito debater os “Contributos do Atletismo e do Voleibol no desenvolvimento de hábitos de vida saudáveis” (ação coletiva) e a abordagem de estratégias pedagógicas relativamente ao “Ensino do Atletismo na Escola” (ação individual). O EP foi uma etapa de aprendizagem fundamental para a nossa formação enquanto professores, sendo uma experiência de grande cumplicidade e partilha pedagógica

On wireless sensors communication for overhead transmission line monitoring in power delivery systems

The transmission of energy is monitored in the smart grid through deploying sensors in all the components, including the overhead transmission lines. There are many poles/towers supporting a long overhead transmission line. Naturally, sensors are deployed on the location close to the poles/towers on each span. Due to the limited transmission range of the wireless transceiver module of a sensor, researchers generally assume that data generated by a sensor have to be delivered to the substation through a set of sensors in-between. This results in a linear network model. In this paper, we first analyze the performance of this model in handling the traffics extracted from an existing testbed. We realize that the linear network model may not be sufficient to support future smart grid applications which may have diversified requirements on data delivery. We then study a new network model in which sensor/relay nodes can also communicate with other nodes using a wide area network such as the cellular network. In this new model, the network formed can be reconfigured based on the application requirements to deliver information to the substations efficiently and effectively.published_or_final_versionThe 1st IEEE International Conference on Smart Grid Communications (SmartGridComm 2010), Gaithersburg, MD., 4-6 October 2010. In Proceedings of the 1st SmartGridComm, 2010, p. 309-31

High recurrence rate supports need for secondary prophylaxis in non-HIV patients with disseminated mycobacterium avium complex infection: a multi-center observational study

© 2016 Sridhar et al.Background: Long-term outcomes in non-HIV immunocompromised patients with disseminated Mycobacterium avium complex (dMAC) infections are unknown and the need for post-treatment secondary prophylaxis against MAC is uncertain in this setting. The objective of this study was to determine the need of continuing secondary anti-MAC prophylaxis in non-HIV patients after completing treatment of the primary dMAC episode. Methods: We conducted a ten-year multi-center analysis of non-HIV immunosuppressed patients with dMAC infections in Hong Kong. Results: We observed sixteen patients with dMAC during the study period of which five (31 %) were non-HIV immunosuppressed patients. In the non-HIV immunosuppressed group, three patients completed a treatment course without secondary prophylaxis, one patient received azithromycin-based secondary prophylaxis and one patient was still receiving therapy for the first dMAC episode. All the three patients who completed treatment without being given secondary prophylaxis developed recurrent dMAC infection requiring retreatment. Conclusions: In view of the high rate of dMAC infection recurrence in non-HIV immunocompromised patients following treatment completion, our data support long-term anti-MAC suppression therapy after treatment of the first dMAC infection episode in immunocompromised non-HIV patients, as is recommended for patients with advanced HIV. Tests of cell mediated immune function need to be evaluated to guide prophylaxis discontinuation in non-HIV patients.published_or_final_versio

Viral Replication in the Nasopharynx Is Associated with Diarrhea in Patients with Severe Acute Respiratory Syndrome

The role of severe acute respiratory syndrome (SARS) coronavirus as an enteric pathogen was investigated in a cohort of 142 patients with SARS who were treated with a standard treatment protocol. Data from daily hematological, biochemical, radiological, and microbiological investigations were prospectively collected, and the correlation of these findings with diarrhea was retrospectively analyzed. Sixty-nine patients (48.6%) developed diarrhea at a mean (± standard deviation [SD]) of 7.6 ± 2.6 days after the onset of symptoms. The diarrhea was most severe at a mean (± SD) of 8.8 ± 2.4 days after onset, with a maximum frequency of 24 episodes per day (median, 5 episodes; range, 3-24 episodes). A higher mean virus load in nasopharyngeal specimens obtained on day 10 after the onset of symptoms was significantly associated with the occurrence of diarrhea (3.1 log 10 vs. 1.8 log 10 copies/mL; P = .01) and mortality (6.2 vs. 1.7 log 10 copies/mL; P<.01). However, diarrhea was not associated with mortality. The lung and the gastrointestinal tract may react differently to SARS coronavirus infection. Additional investigation of the role of SARS coronavirus in the pathogenesis of diarrhea in patients with SARS should be conducted.published_or_final_versio

Modeling the effect of age in T1-2 breast cancer using the SEER database

BACKGROUND: Modeling the relationship between age and mortality for breast cancer patients may have important prognostic and therapeutic implications. METHODS: Data from 9 registries of the Surveillance, Epidemiology, and End Results Program (SEER) of the United States were used. This study employed proportional hazards to model mortality in women with T1-2 breast cancers. The residuals of the model were used to examine the effect of age on mortality. This procedure was applied to node-negative (N0) and node-positive (N+) patients. All causes mortality and breast cancer specific mortality were evaluated. RESULTS: The relationship between age and mortality is biphasic. For both N0 and N+ patients among the T1-2 group, the analysis suggested two age components. One component is linear and corresponds to a natural increase of mortality with each year of age. The other component is quasi-quadratic and is centered around age 50. This component contributes to an increased risk of mortality as age increases beyond 50. It suggests a hormonally related process: the farther from menopause in either direction, the more prognosis is adversely influenced by the quasi-quadratic component. There is a complex relationship between hormone receptor status and other prognostic factors, like age. CONCLUSION: The present analysis confirms the findings of many epidemiological and clinical trials that the relationship between age and mortality is biphasic. Compared with older patients, young women experience an abnormally high risk of death. Among elderly patients, the risk of death from breast cancer does not decrease with increasing age. These facts are important in the discussion of options for adjuvant treatment with breast cancer patients

Four Generations: SUSY and SUSY Breaking

We revisit four generations within the context of supersymmetry. We compute the perturbativity limits for the fourth generation Yukawa couplings and show that if the masses of the fourth generation lie within reasonable limits of their present experimental lower bounds, it is possible to have perturbativity only up to scales around 1000 TeV. Such low scales are ideally suited to incorporate gauge mediated supersymmetry breaking, where the mediation scale can be as low as 10-20 TeV. The minimal messenger model, however, is highly constrained. While lack of electroweak symmetry breaking rules out a large part of the parameter space, a small region exists, where the fourth generation stau is tachyonic. General gauge mediation with its broader set of boundary conditions is better suited to accommodate the fourth generation.Comment: 27 pages, 5 figure